How to turn any mesh into its bounding box
Bmesh script

Quick, n  dirty little bmesh script to do this. For all mesh objects in the screen replace the mesh with the box created from the eight corners of the bounding box.


I've used the convex hull operator which produces a triangulated
mesh.
Current version replaces mesh with hull.
As always save before, and / or test on a copy.


script

import bpy
import bmesh
context = bpy.context
scene = context.scene
bm = bmesh.new()
mesh_obs = [o for o in scene.objects if o.type == 'MESH']
for ob in mesh_obs:
    me = ob.data 
    #me = ob.data.copy() # create a copy

    verts = [bm.verts.new(b) for b in ob.bound_box]
    bmesh.ops.convex_hull(bm, input=verts)
    bm.to_mesh(me)
    ob.data = me # needed if copy
    bm.clear()
bm.free()